JP7315235B2 - antenna device - Google Patents

Description

The present invention relates to an antenna device.

There are antennas such as inverted L antennas, inverted F antennas, and T-shaped antennas in which a monopole antenna is mounted on the substrate GND. The advantage of these antennas is that they can be made smaller than dipole antennas. For example, Patent Document 1 describes an inverted L-shaped monopole antenna.

However, since the directivity of these antennas varies depending on the size of the substrate GND, it has been difficult to provide directivity in a specific direction.

The change in directivity of a monopole antenna will be described below in comparison with a dipole antenna.

11 and 12 are perspective views showing an example of a model in which a dipole antenna is mounted on a device substrate. The antenna shown in FIG. 12 has a longer GND length in the Z direction than the antenna shown in FIG.

13 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna of FIG. 11. FIG. FIG. 14 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna of FIG.

There is little difference between the radiation pattern of FIG. 13 and the radiation pattern of FIG. This is because, in the case of a dipole antenna, as shown in FIGS. 15 and 16, the antenna current 11 predominantly flows through the antenna section 12 and hardly flows through the substrate GND13. 15 is a diagram showing the antenna current in the antenna device of FIG. 11. FIG. 16 is a diagram showing the antenna current in the antenna device of FIG. 12. In FIG.

Next, the radiation pattern and antenna current of a monopole antenna will be explained. 17 and 18 are perspective views showing an example of a model in which a monopole antenna is mounted on a device substrate. 17 and 18, a T-shaped antenna 21, which is one of monopole antennas, is mounted on the device substrate 22. In FIG. The antenna shown in FIG. 18 has a longer GND length in the Z direction than the antenna shown in FIG.

19 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna of FIG. 17. FIG. FIG. 20 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna of FIG.

Unlike the radiation patterns of the dipole antennas of FIGS. 13 and 14, the radiation pattern of FIG. 20 is smaller than the radiation pattern of FIG.

In the case of a monopole antenna, the radiation pattern changes due to the antenna current 24 flowing through the substrate GND23. 21 is a diagram showing the antenna current in the antenna device of FIG. 17. FIG. Also, FIG. 22 is a diagram showing the antenna current in the antenna device of FIG.

As shown in FIG. 21, when the length including the antenna and substrate GND is λ/2 with respect to the operating frequency, the antenna current 24 flows in one direction. Therefore, as shown in FIG. 19, the radiation pattern on the XY plane is almost the same as that of the dipole antenna.

However, when the length of the substrate GND changes from λ/2 as shown in FIG. 18, an anti-phase antenna current 25 is generated in the substrate GND 23 as shown in FIG. As a result, the radiation pattern in the XY plane of the antenna of FIG. 16 has a smaller vertically polarized wave in the XY plane as shown in FIG.

WO2012/053282

Thus, the monopole antenna has a problem that the directivity of the antenna changes depending on the length of the substrate. Also, it is difficult to match the length of the substrate to the antenna in terms of device design.

Even if the length of the substrate can be matched, if the cable or the like is pulled out as shown in FIG. 23, depending on the length of the cable, an antenna current of opposite phase is generated as shown in FIG. FIG. 25 shows a radiation pattern of vertically polarized waves in the XY plane of the antenna device of FIG. As shown in FIG. 25, the radiation pattern in the XY plane is reduced as in FIG.

An antenna device according to a specific embodiment includes a monopole antenna, a substrate having an electronic circuit, and a GND conductive pattern provided on one surface of the substrate, and has a split-ring resonator shape on the periphery of the GND conductive pattern.

According to the antenna device of the present invention, even when a monopole antenna is mounted on a substrate, the desired antenna directivity of the split ring resonator can be obtained without worrying about the size of the substrate, the conductor such as a cable, and the like.

1 is a perspective view showing an example of an antenna device according to a first embodiment; FIG. 4 is a diagram showing the shape of the split ring portion of the antenna device according to the first embodiment; FIG. 4 is a diagram showing antenna currents in the antenna device according to the first embodiment; FIG. 3 is a diagram showing a radiation pattern of the antenna device according to the first embodiment; FIG. It is a perspective view which shows an example of an antenna device. It is a figure which shows the antenna current in an antenna device. It is a figure which shows the radiation pattern of an antenna device. FIG. 11 is a perspective view showing an example of an antenna device according to a second embodiment; FIG. 9 is a diagram showing antenna currents in the antenna device according to the second embodiment; FIG. 10 is a diagram showing a radiation pattern of the antenna device according to the second embodiment; FIG. FIG. 4 is a perspective view showing an example of a model in which a dipole antenna is mounted on a device substrate; FIG. 4 is a perspective view showing an example of a model in which a dipole antenna is mounted on a device substrate; FIG. 12 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna of FIG. 11; FIG. 13 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna of FIG. 12; FIG. 12 is a diagram showing an antenna current in the antenna device of FIG. 11; 13 is a diagram showing an antenna current in the antenna device of FIG. 12; FIG. FIG. 4 is a perspective view showing an example of a model in which a monopole antenna is mounted on a device substrate; FIG. 4 is a perspective view showing an example of a model in which a monopole antenna is mounted on a device substrate; FIG. 18 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna of FIG. 17; FIG. 19 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna of FIG. 18; 18 is a diagram showing an antenna current in the antenna device of FIG. 17; FIG. FIG. 19 is a diagram showing an antenna current in the antenna device of FIG. 18; FIG. 4 is a perspective view showing an example of an antenna from which a cable or the like is pulled out; 24 is a diagram showing an antenna current in the antenna device of FIG. 23; FIG. FIG. 24 is a diagram showing a radiation pattern of vertically polarized waves in the XY plane of the antenna device of FIG. 23;

(Embodiment 1)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of an antenna device according to Embodiment 1. FIG. In FIG. 1, the antenna device 100 includes an antenna section 101, a substrate 102, and a GND conductive pattern 103. FIG.

The antenna section 101 is a monopole antenna in which a rod-shaped conductor is extended from a feeding point. The antenna section 101 is connected to one feeding point 104 and functions as a monopole antenna. The antenna section 101 may have branches, bends, or the like. In FIG. 1, the antenna section 101 has a T shape in which two straight lines intersect.

The substrate 102 is a substrate having a GND conductive pattern 103 on one surface. Substrate 102 may be, for example, a printed circuit board. Also, the substrate 102 may have an electronic circuit. For example, the substrate 102 may be a substrate that is connected to the antenna section 101 and has a circuit that processes radio signals received by the antenna section 101 . Also, the substrate 102 may be a substrate having a circuit for processing radio signals transmitted from the antenna section 101 . It is desirable that the substrate 102 has a size such that the length from the end of the antenna 101 to the aperture is at least half the wavelength of the communication frequency.

The GND conductive pattern 103 is, for example, a rectangular metal layer formed on one surface of the substrate 102 and is a layer of reference potential. Also, the GND conductive pattern 103 may be formed on any layer of the multilayer substrate.

The GND conductive pattern 103 has a first split ring portion 131 and a second split ring portion 132 . The length from the openings of the first split ring portion 131 and the second split ring portion 132 to the end portion 111 of the antenna portion 101 via the periphery of the GND conductive pattern 103 is half the wavelength of the communication frequency. That is, the openings of the first split ring part 131 and the second split ring part 132 are arranged at the position where the antenna current is inverted in FIG. In the example of FIG. 1, the GND conductive pattern 103 has a rectangular shape, and a first split ring portion 131 and a second split ring portion 132 are formed on two parallel sides of the GND conductive pattern 103, respectively.

For example, when the communication frequency is 2.4 GHz, the size and slit length of the first split ring part 131 and the second split ring part 132 may be adjusted so as to resonate at 2.4 GHz.

FIG. 2 is a diagram showing the shape of the split ring portion of the antenna device according to the first embodiment. The first split ring part 131 and the second split ring part 132 have the shape shown in FIG.

The first split ring part 131 has an annular shape surrounding a space 133 where the metal layer of the GND conductive pattern 103 does not exist, and has an opening 135 on a side 134 of the GND conductive pattern 103 . The second split ring part 132 also has the same shape as the first split ring part 131 .

FIG. 3 is a diagram showing antenna currents in the antenna device according to the first embodiment. In FIG. 3, since the first split ring part 131 and the second split ring part 132 are arranged, the opposite antenna currents 141 and 142 are greatly reduced.

FIG. 4 is a diagram showing radiation patterns of the antenna device according to the first embodiment. As shown in FIG. 4, the vertical polarization in the XY plane is greatly improved, and radiation patterns close to those shown in FIGS. 13 and 14 can be obtained.

As described above, the antenna device according to the first embodiment suppresses the antenna current flowing in the opposite phase by placing the split ring resonator at the position where the antenna current of the substrate GND is desired to be controlled.

As a result, regardless of the feeding antenna, the antenna current flowing on the substrate can be adjusted by the split ring resonator to control the antenna gain.

As described above, according to the antenna device of Embodiment 1, even when a monopole antenna is mounted on the substrate, the desired antenna directivity can be obtained without worrying about the substrate size, the conductor such as the cable, etc., by mounting the split ring resonator at a position separated by λ/2 including the antenna.

(Embodiment 2)
In Embodiment 2, an example in which a monopole antenna is an inverted L antenna will be described. First, when an inverted L antenna, which is one of monopole antennas, is placed on a substrate as shown in FIG. 5, the radiation pattern of horizontally polarized waves in the XZ plane becomes the shape shown in FIG. It can be seen that the antenna shown in FIG. 5 is unsuitable for use as an antenna that must have a stable gain in the range indicated by the arrow, for example, as a GPS antenna with the Z direction as the sky direction.

The cause of the formation of the radiation pattern in FIG. 6 is the reverse running antenna current as shown in FIG.

FIG. 8 is a perspective view of an example of the antenna device according to the second embodiment. In FIG. 8, an antenna device 200 includes an antenna section 201, a substrate 102, and a GND conductive pattern 203. FIG. The GND conductive pattern 203 has a first split ring part 231 and a second split ring part 232 . The length from the opening of the first split ring part 231 to the edge of the antenna part 201 via the periphery of the GND conductive pattern 103 is half the wavelength of the communication frequency. Also, the length from the second split ring part 232 to the end of the antenna part 201 via the periphery of the GND conductive pattern 103 is shorter than half the wavelength of the communication frequency.

The antenna part 201 has a shape extending in the Z-axis direction from the feeding point and having an end extending in the X-axis direction. The antenna section 201 is connected to one feeding point and functions as a monopole antenna.

An image of the antenna current of the antenna device 200 is shown in FIG. FIG. 9 is a diagram showing antenna currents in the antenna device according to the second embodiment. As shown in FIG. 9, the current component with the opposite phase is smaller in the X direction, and the current in the Z direction is also smaller.

FIG. 10 is a diagram showing radiation patterns of the antenna device according to the second embodiment. Compared to the radiation pattern of FIG. 6, the radiation pattern of FIG.

As described above, according to the antenna device of Embodiment 2, even if the two sides of the GND conductive pattern that intersect at right angles each have a split-ring resonator shape, the desired antenna directivity can be obtained without worrying about the size of the substrate, conductors such as cables, and the like.

Further, according to the antenna apparatus of the second embodiment, a new effect of obtaining desired directivity by mounting a split ring resonator is obtained without separating the distance of λ/2 including the antenna.

It should be noted that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the scope of the invention. For example, the shape of the open ring forming the split ring resonance portion is not particularly limited as long as it has open ends, and may be a circle, an ellipse, a square, a polygon, or a combination thereof.

Also, although monopole antennas such as T-shaped and inverted L-shaped antennas have been described as examples, any feeding antenna can be applied as long as it is an antenna device that controls the antenna current on the substrate GND with a split ring resonance section.

Also, the substrate may further comprise other electronic circuits. For example, a communication circuit connected to the antenna may be provided. Also, it may be applied to a multi-layer substrate.

In addition, if the two openings of the split ring resonator cannot secure the length from the opening of the split ring resonator shape to the end of the antenna via the periphery of the GND conductive pattern, one opening may be provided at a position where the length is from the opening to the end of the antenna via the periphery of the GND conductive pattern, and the other opening may be provided near the feeding point of the monopole antenna. In this case, the size of the substrate should be such that one opening can be the length from the opening to the edge of the antenna via the periphery of the GND conductive pattern.

100, 200 Antenna device 200
101, 201 antenna section 102 substrate 103, 203 GND conductive pattern 131, 231 first split ring section 132, 232 second split ring section

Claims (3)

A monopole antenna, a substrate with an electronic circuit, and a GND conductive pattern provided on one surface of the substrate,
having a split-ring resonator shape on the periphery of the GND conductive pattern,
The length from the opening of the split ring resonator shape to the end of the antenna via the periphery of the GND conductive pattern is half the wavelength of the communication frequency,
The GND conductive pattern has a shape having at least two parallel sides,
each having the split ring resonator shape so as to be paired with the two sides of the GND conductive pattern
antenna device. A monopole antenna, a substrate with an electronic circuit, and a GND conductive pattern provided on one surface of the substrate,
having a split-ring resonator shape on the periphery of the GND conductive pattern,
The length from the opening of the split ring resonator shape to the end of the antenna via the periphery of the GND conductive pattern is half the wavelength of the communication frequency,
The GND conductive pattern has a shape having at least two orthogonal sides,
Each of the two orthogonal sides has the split ring resonator shape.
antenna device . one of the two orthogonal sides has a length from the opening of the split -ring resonator shape to the end of the antenna via the periphery of the GND conductive pattern is half the wavelength of the communication frequency ;
3. The antenna device according to claim 2 , wherein the length from the opening of the split-ring resonator shape on the other side to the edge of the antenna via the periphery of the GND conductive pattern is shorter than half the wavelength of the communication frequency.

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